How save canvas state to db?

So I built this real-time drawing app with node.js, socket.io, and html5 canvas. Every pixel that the mouse is moved while clicked is tracked and broadcast (to displ开发者_如何学编程ay drawing input on other computers).

I know it is possible to save an image of the canvas but this canvas is very large (10000x10000+ pixels). Right now, when the page is refreshed all the drawings are gone (as it was just send over a socket, nothing saved).

I would like to save all the canvas data to a db and then somehow rewrite it when the page is loaded again, but it is simply too much. How would you go about doing this??

You can track the clicks and mouse moves that made the canvas look that way while you're sending them over the socket, and simulate them to rebuild the image.